The present invention relates to a rotary electric machine control system including a rotary electric machine and an inverter interposed between a battery and the rotary electric machine to control a current that flows through the rotary electric machine.
WO2003/056694 discloses an electrical load apparatus 100 including a battery B, an AC motor M1 serving as a rotary electric machine, and an inverter 14 interposed between the battery and the rotary electric machine to control a current that flows through the rotary electric machine.
In the electrical load apparatus 100, when the amount of increase (equivalent to the “variation rate” in the present application) in power consumed by the AC motor M1 (equivalent to the “battery electric power” in the present application) exceeds allowable power that can be supplied from a capacitance 13 to the inverter 14, a control device 30 limits the amount of increase in power consumed by the AC motor M1 to a range in which continuous driving of the electrical load apparatus 100 is allowed.
The technique disclosed in WO2003/056694 is related to a vehicle or the like that runs on a drive force produced by the AC motor M1, and is intended to protect the inverter by limiting the amount of increase in consumed power to a predetermined range.
Nowadays, hybrid systems including an engine and a rotary electric machine serving as a motor as drive sources to obtain a drive force for running from one or both of the engine and the rotary electric machine are in practical use. As one type of hybrid system, a so-called split hybrid system is provided which includes an engine and a pair of rotary electric machines, and in which a drive force output from the engine is distributed to wheels and a first one of the rotary electric machines to cause the first rotary electric machine to generate electricity while a second rotary electric machine supplements the engine drive force to be transmitted to the wheels. In the system, the engine is operated in accordance with an optimum fuel efficiency line to allow the vehicle to run at a very high fuel efficiency. In the system, the second rotary electric machine mainly serves as a motor.
In this type of hybrid system, a rotary electric machine which mainly produces a torque for driving the wheels (the second rotary electric machine which serves as a motor described earlier) and a rotary electric machine which mainly controls the rotational speed of the engine (the first rotary electric machine which serves as a generator described earlier) are connected in parallel to a single battery via an inverter. The rotary electric machines are controlled such that the sum of electric power consumed by the rotary electric machine serving as a motor and electric power consumed by the rotary electric machine serving as a generator will not exceed the discharge electric power limit of the battery.